It is an irony of the 2008 election that the long shadow of Jack Abramoff, the former Republican super-lobbyist, looms over the very man, John McCain, whose Senate investigations paved the way for his conviction on corruption and fraud charges two years ago.

Barack Obama, the presumptive Republican nominee's likely Democratic rival for the White House, has made eradicating Washington's "culture of corruption" a core theme of his campaign and a point of attack against Mr McCain.